The invention relates to a device for transmitting color television signals, which contains a luminance signal, and at least one color signal assigned to the luminance signal for transmission. Such a device is described in patent application DE-A1 42 15 007, not published before the priority date of this invention. The professional can find an interference suppressing device in the unpublished publication, which is located in a transmitting device for transmitting the chrominance in a color television signal. The interference suppressing device contains a delay line in the transmission path of the chrominance signal, where one end of an signal fade over circuit is connected to the input, and the other end to the output in such a way, that in both end positions of the signal fade over circuit the input or the output of the delay line is directly connected to the output of the signal fade over circuit. The signal fade over circuit may be a switch or an electronic potentiometer and is controlled by a control signal that oscillates around a zero line, and which has two opposing semi-oscillations, and crosses the zero line with a steep zero passage between the two semi-oscillations. This zero passage defines an instant of a detection device that consists of two signal jump detectors and a signal subtracter. According to the publication, each signal jump detector consists of a delay line and a differential amplifier connected on the input side between the input and the output of the delay line, and whose output is connected to one of the signal subtracter inputs. The delay time of both series-connected delay lines of the two signal jump detectors is designed, so that it is an odd-numbered multiple of half the oscillation time of the color carrier oscillation of the transmitted color signal on one side, and is slightly larger on the other side than the largest anticipated rise time of the color signal slope, namely the time of the phase change of a first color phase to a second color phase corresponding to the color carrier signal. In the cited publication, the length of the delay time is oriented exclusively to the type of transmission of a color signal or signals in a color television transmission, namely to the transmission of the color by the phase of a color carrier oscillation of a predetermined, constant frequency. A delay element, connected upstream of the interference suppressing device, only produces a time coordination between the transmitted luminance signal and the colors of the transmitted color television signal. Other signals with flattened transitions which must be transmitted, are not considered in the design of the delay line time in both the signal fading over and the signal jump detection.
When a jump edge of a signal is transmitted in a transmission system or in a transmitting device with a limited bandwidth, not only is the jump edge flattened in a signal slope of a clear slope period, which is about half the period of the bandwidth frequency of the transmitting device, but additionally an overshoot follows the flattened jump edge, and grows out of the signal slope. This overshoot, which is superimposed on the transmitted signal, has nearly the same frequency as the bandwidth of the transmitting device, and can lead to considerable interference in the jump edge with the information transmitted by the signal. Thus, in the transmission of sound, high-frequency sound noises are thereby heavily discolored or distorted, or interfering edge echoes, so-called ringing, takes place in the vertical luminance edges of a video transmission, because of the distortion effect.
U.S. Pat. No. 4,758,891 discloses a method and apparatus for improving the rise and fall time of a video signal using an undelayed signal, a delayed signal and a further delayed signal.
The edges of a video signal are sharpened by switching the output furnishing the sharpened signal in sequence first to receive a signal delayed by a greater amount, i.e. a signal which has not as yet undergone transition, and, secondly, to receive a signal delayed by a lesser amount, i.e. one that has already completed the transition. The rise time of the affected edge thus depends only on the time required to switch from one terminal to the next. The same switching sequence is carried out regardless of whether the transition is a negative going or positive going transition.
Since the system of the U.S. Pat. No. 4,758,891 uses an electronics witch which is switching between two time delay lines the output signal is most of the time delayed.
In the case of using this system for regenerating of video luminance signal the video chrominance signal must be delayed also. That makes the solution expensive when realized in an integrated circuit for example in a video processor.